"""Thematic transformations used by the existing complete-draft composer.

Source features initialize a heard theme. Subsequent complete routes develop
that realization, conditioned on the actual incoming musical state.
"""
from __future__ import annotations

import dataclasses
from fractions import Fraction as F

import generator.model
import generator.harmony
import generator.vocabulary
from generator.solo import types, policy, sequences, routes, features as references, similarity, phrasing, profiles


def source_notes(analysis):
  return tuple(dataclasses.replace(n,start=max(F(),n.start-analysis.body_offset),end=n.end-analysis.body_offset,
    event_id=n.sources[0],position=None) for n in analysis.melody if n.end>analysis.body_offset)



def silence(source,incoming,part,harmony,tempo,seed):
  from generator.solo import realization
  motif=types.Motif('intentional_space',(),source.end-source.start,(),'explicit missing harmony')
  plan=types.PhrasePlan(part+'_'+source.id,source.start,source.end,motif,'space','thematic_recomposition',None,harmony.profile.register,F(),F(),
    (types.ActivitySpan(source.start,source.end,'space',F(),F()),),passage_id=source.id,passage_start=source.start,passage_end=source.end)
  draft=types.MelodicDraft(plan.id,source.start,source.end,(),(),(),(),(),incoming.home,'space',source_phrase=source,source_reference=incoming.source_reference)
  phrase=realization.checked_phrase(plan,draft,(),incoming.treatments,incoming,harmony,tempo)
  if phrase is None:return ()
  state=dataclasses.replace(phrase.state,home=incoming.home,source_reference=incoming.source_reference,callbacks=incoming.callbacks,
    history=incoming.history,returns=incoming.returns,closures=incoming.closures,register_peak=incoming.register_peak)
  original=dataclasses.replace(draft,notes=source.notes)
  return (dataclasses.replace(phrase,state=state,initial=original,refined=draft,score=0.),)


def short_fragment(source,incoming,part,harmony,tempo,seed,final):
  """An explicitly reduced pickup around missing harmony; not a new theme."""
  from generator.solo import leads,realization
  reference=incoming.home.notes if incoming.home else source.notes
  if not reference:return ()
  template=dataclasses.replace(reference[0],start=source.start,end=source.end,position=None,continuation=False,event_id=source.id+':reduction')
  result=[]
  for pitch in pitches(harmony,template,incoming.last.pitch.number() if incoming.last else template.pitch.number(),members=True):
    note=dataclasses.replace(template,pitch=pitch)
    motif=types.Motif('reduction',reference,source.end-source.start,(),'explicit short fragment; no claim of full motif fidelity')
    anchor=types.Anchor(note.event_id+':arrival',note.start,note.start,pitch,harmony.members(note.start,note.end),harmony.profile.register,note.end-note.start,'terminal' if final else 'intermediate',harmony.at(note.start).chord,hold_until=note.end)
    transform=types.Transformation(note.event_id,reference[0].event_id,incoming.home.id if incoming.home else '', 'fragment',note.start,note.end,(note.event_id,),((F(),note.end-note.start),),preserves=())
    draft=types.MelodicDraft(part+'_'+note.event_id,source.start,source.end,(note,),(transform,),(note.event_id,),(),(anchor,),incoming.home,'fragment',source_phrase=source,source_reference=incoming.source_reference)
    plan=types.PhrasePlan(draft.id,source.start,source.end,motif,'fragment','thematic_recomposition',None,harmony.profile.register,F(5,4),F(),ending='sustain' if final else 'connected',closure='closed' if final else 'open',passage_id=source.id,passage_start=source.start,passage_end=source.end)
    phrase=realization.checked_phrase(plan,draft,(note,),incoming.treatments,incoming,harmony,tempo)
    if phrase:
      state=dataclasses.replace(phrase.state,home=incoming.home,source_reference=incoming.source_reference,callbacks=incoming.callbacks,
        history=incoming.history,returns=incoming.returns,closures=incoming.closures,register_peak=incoming.register_peak)
      result.append(dataclasses.replace(phrase,state=state,initial=draft,refined=draft))
  return tuple(result)


def seeds(analysis, bar, seed):
  melody=tuple(dataclasses.replace(n,start=n.start-analysis.body_offset,end=n.end-analysis.body_offset,
    event_id=n.sources[0]) for n in analysis.melody)
  groups=[]
  for i in range(len(melody)):
    for count in ((len(melody),) if len(melody)<3 else (3,4,5,6,7,8)):
      group=melody[i:i+count]
      if len(group)!=count or group[-1].end-group[0].start>max(2*bar,F(3)):
        continue
      local=tuple(dataclasses.replace(n,start=n.start-group[0].start,end=n.end-group[0].start) for n in group)
      parent=next((s.id for s in analysis.source_phrases if s.start<=max(0,group[0].start)<s.end),'pickup')
      for treatment in generator.vocabulary.role().get('preferred_features',('rhythmic_seed','contour_seed','opening_fragment','characteristic_interval')):
        identity=policy.stable_rank(seed,(group,treatment))[:12]
        groups.append(types.SourceReference(identity,parent,group[0].start,group[-1].end,local,treatment))
  def rank(ref):
    rhythm={(n.start,n.end-n.start) for n in ref.notes}
    intervals={b.pitch.number()-a.pitch.number() for a,b in zip(ref.notes,ref.notes[1:])}
    preferred=generator.vocabulary.role().get('preferred_features',[])
    preference=preferred.index(ref.treatment) if ref.treatment in preferred else 0
    turn=any(a*b<0 for a,b in zip(ref.notes and tuple(b.pitch.number()-a.pitch.number() for a,b in zip(ref.notes,ref.notes[1:])),tuple(b.pitch.number()-a.pitch.number() for a,b in zip(ref.notes,ref.notes[1:]))[1:]))
    return (-min(4,len(intervals))-.3*turn+.15*preference,-min(3,len(rhythm)),ref.id)
  return sequences.diverse(groups,rank,lambda r:(r.treatment,int(max(0,r.start)//(4*bar))),policy.DEFAULT.theme_seed_limit)


def feature(reference, actual, *, treatment=None):
  treatment=treatment or reference.treatment
  required={'rhythmic_seed':('rhythm',),'contour_seed':('contour',),
    'opening_fragment':('rhythm','pitches'),'characteristic_interval':('exact_intervals',),
    'repeat_with_harmonic_adaptation':('rhythm','contour'),'answer':('contour',),
    'extend':('contour',),'fragment':('rhythm',),'callback':('rhythm','pitches'),
    'return':('rhythm','intervals'), 'develop_rhythm':('rhythm',),
    'develop_contour':('intervals',), 'continue':('contour',)}[treatment]
  original=reference.notes
  authored=next((r for r in generator.vocabulary.data('grammar')['transformations'] if r['id']==treatment),None)
  if authored:required=tuple(authored['preserve'])
  origin=original[0].start
  octave=12*round((actual[0].pitch.number()-original[0].pitch.number())/12)
  return types.IdentifyingFeature(reference.id+':'+treatment,tuple(n.event_id for n in actual),
    tuple((n.start-origin,n.end-n.start) for n in original),
    tuple(b.pitch.number()-a.pitch.number() for a,b in zip(original,original[1:])),reference.id,required,
    tuple(n.pitch.number()+octave for n in original))


def rhythmic_purpose(operation, terminal=False):
  if terminal:return 'arrival'
  if operation in ('introduce','callback','return','repeat_with_harmonic_adaptation'):return 'entrance'
  if operation in ('answer','fragment'):return 'answer'
  return 'connect' if operation=='continue' else 'continue'


def rhythm_cost(pattern,length,purpose):
  """Evaluate a rhythmic job, not resemblance to any target score or density."""
  if not pattern:return float('inf')
  gaps=[b[0]-a[1] for a,b in zip(pattern,pattern[1:])]
  isolated=sum(b-a<=F(1,2) and prev[1]<a and b<nxt[0]
    for prev,(a,b),nxt in zip(pattern,pattern[1:],pattern[2:]))
  values={b-a for a,b in pattern}
  uniform=.15 if len(pattern)>=4 and len(values)==1 else 0.
  if purpose in ('continue','connect'):
    # Silence may articulate an idea; disconnected tiny islands do not carry
    # unfinished motion. No minimum occupancy or chorus attack quota.
    return isolated+.25*float(sum(gaps,F())/length)+uniform
  if purpose=='arrival':
    return isolated+float(max(F(),F(1)- (pattern[-1][1]-pattern[-1][0])))/2+uniform
  return isolated+uniform


def rhythm_windows(library,meter,length,context,purpose='continue'):
  from generator.solo import drafts
  tempo=getattr(context,'tempo',120)
  key=('theme-rhythm',id(library),meter,length,tempo,purpose)
  if key not in context.pools:
    patterns={}
    bar=F(meter.split('/')[0])*4/int(meter.split('/')[1])
    if length>bar:
      # The two-bar catalog contains quarter-note masks. Include combinations
      # of the richer one-bar material as complete timing alternatives, rather
      # than accidentally excluding eighths/dotted values by snippet length.
      # Pitch paths and feature contracts span the assembled rhythm's seams.
      split=bar
      for left,left_id in rhythm_windows(library,meter,split,context,'continue' if purpose=='arrival' else purpose):
        for right,right_id in rhythm_windows(library,meter,length-split,context,purpose):
          combined=(*left,*((a+split,b+split) for a,b in right))
          if len(combined)<=16:patterns.setdefault(combined,left_id+' + '+right_id)
    for identifier,pattern,total in drafts.catalog(library,meter):
      if total<length:continue
      for offset in sorted({F(),*(a for a,_ in pattern)}):
        if offset+length>total or any(a<offset<b or a<offset+length<b for a,b in pattern):continue
        selected=tuple((a-offset,b-offset) for a,b in pattern if offset<=a and b<=offset+length)
        if selected and len(selected)<=16:patterns.setdefault(selected,identifier)
    # Authored cells can start late and continue over computational barlines.
    for cell in generator.vocabulary.rhythm_cells(tempo,purpose):
      identifier,pattern,total=cell.id,cell.pattern,cell.duration
      if total>length:continue
      for offset in (F(),F(1,2),max(F(),length-total)):
        if offset+total>length:continue
        head=tuple((a+offset,b+offset) for a,b in pattern)
        # Keep representative compatible continuations; never let dictionary
        # insertion order secretly choose the only tail for an authored cell.
        tails=sequences.diverse(tuple(patterns),lambda p:(rhythm_cost(p,length,purpose),policy.stable_rank('rhythm-tail',p)),
          lambda p:(len(p),p[-1][1]-p[-1][0]),2) or ((),)
        for tail in tails:
          if any(a<offset+total<b for a,b in tail):continue
          combined=(*head,*((a,b) for a,b in tail if a>=offset+total))
          if 2<=len(combined)<=16:patterns.setdefault(combined,'authored:'+identifier)
    context.pools[key]=sequences.diverse(tuple(patterns.items()),
      lambda x:(rhythm_cost(x[0],length,purpose)+(0 if x[1].startswith('authored:') else .05),policy.stable_rank('rhythm-window',x[0])),
      lambda x:(x[1].startswith('authored:'),len(x[0]),x[0][0][0],any(a[1]!=b[0] for a,b in zip(x[0],x[0][1:]))),8)
  return context.pools[key]


def patterns(ref, start, finish, rhythms, meter, context, *, home=None, operation='introduce', terminal=False, ending=None):
  length=finish-start; values={}
  purpose=rhythmic_purpose(operation,terminal)
  if home and operation in ('repeat_with_harmonic_adaptation','return'):
    pattern=tuple((n.start,n.end) for n in home.notes if n.end<=length)
    if pattern:values[pattern]='heard-theme'
  prefix=tuple((n.start,n.end) for n in ref.notes)
  fixed_rhythm=ref.treatment in ('rhythmic_seed','opening_fragment','callback') or operation in ('fragment','repeat_with_harmonic_adaptation','return','develop_rhythm')
  if fixed_rhythm:
    duration=prefix[-1][1]
    if duration==length:values[prefix]=ref.id
    if duration<length:
      for tail,label in rhythm_windows(rhythms,meter,length-duration,context,purpose):
        values[(*prefix,*((a+duration,b+duration) for a,b in tail))]=ref.id+' + '+label
  else:
    values.update(rhythm_windows(rhythms,meter,length,context,purpose))
  if home and operation=='answer':
    for p,label in rhythm_windows(rhythms,meter,length,context,purpose):values.setdefault(p,label)
  if not fixed_rhythm:
    # Develop the heard timing, preserving total duration. Eighth/quarter/dotted
    # alternatives are actual contracts, not failed copies of a rhythmic seed.
    for original,label in tuple(values.items()):
      for i,(a,b) in enumerate(original):
        if b-a==1:
          values[(*original[:i],(a,a+F(1,2)),(a+F(1,2),b),*original[i+1:])]=label+'; diminution'
      for i,((a,b),(c,d)) in enumerate(zip(original,original[1:])):
        if b!=c:continue
        for split in (a+F(1,2),a+F(3,2),d-F(1,2)):
          if a<split<d:
            values[(*original[:i],(a,split),(split,d),*original[i+2:])]=label+'; rhythmic alteration'
  if ending:
    arrivals={}
    arrival=ending.earliest-start
    for original,label in values.items():
      head=tuple((a,min(b,arrival)) for a,b in original if a<arrival)
      if len(head)>=len(ref.notes):
        arrivals[(*head,(arrival,ending.hold_until-start))]=label+'; planned sustained close'
    values=arrivals
  return sequences.diverse(tuple(values.items()),lambda x:(rhythm_cost(x[0],length,purpose),policy.stable_rank(ref.id,x[0])),
    lambda x:(len(x[0]),tuple(b-a for a,b in x[0][:3]),x[0][0][0]),policy.DEFAULT.theme_rhythm_alternatives)


def pitches(harmony,note,base,*,members=False,limit=6,incoming=None):
  from generator.solo.leads import available
  domain=available(harmony,note.start,note.end,members=members or note.end-note.start>=2)
  if members:
    return phrasing.destination_options(domain,lambda p:(phrasing.destination_cost(p,note.start,note.end,harmony,incoming,base),p.number()),
      lambda p:p,lambda p:note.start,harmony,limit)
  return sequences.diverse(domain,lambda p:(abs(p.number()-base),p.number()),
    lambda p:((p.number()-base>0)-(p.number()-base<0),p.number()//12),limit)


def relative_steps(notes,harmony):
  result=[]
  for a,b in zip(notes,notes[1:]):
    scale=harmony.at(b.start).scale
    try:step=types.scale_index(scale,b.pitch.number())-types.scale_index(scale,a.pitch.number())
    except ValueError:
      lo,hi=sorted((a.pitch.number(),b.pitch.number()))
      intervening=range(lo+1,hi+1) if b.pitch.number()>a.pitch.number() else range(lo,hi)
      count=sum(p%12 in scale.pitches for p in intervening)
      step=count if b.pitch.number()>a.pitch.number() else -count
    result.append(step)
  return tuple(result)


def instantiate(templates,first,steps,harmony):
  result=[dataclasses.replace(templates[0],pitch=first)]
  for note,step in zip(templates[1:],steps):
    span=harmony.at(note.start)
    if not span or not span.scale:return ()
    options=routes.advance(span.scale,result[-1].pitch.number(),step)
    if not options:return ()
    p=options[0]
    if not harmony.profile.permits(p.number()) or p.number()%12 not in types.permitted(harmony.choices,note.start,note.end):return ()
    result.append(dataclasses.replace(note,pitch=p))
  return tuple(result) if len(result)==len(templates) else ()


def prefix_paths(templates,ref,first,harmony,library):
  if not hasattr(harmony,'theme_prefixes'):harmony.theme_prefixes={}
  key=(templates[:len(ref.notes)],ref,first,id(library))
  if key not in harmony.theme_prefixes:
    harmony.theme_prefixes[key]=_prefix_paths(templates,ref,first,harmony,library)
  return harmony.theme_prefixes[key]


def _prefix_paths(templates,ref,first,harmony,library):
  count=len(ref.notes); original=ref.notes
  if count==1:return ((dataclasses.replace(templates[0],pitch=first),),)
  if ref.treatment in ('opening_fragment','characteristic_interval','callback'):
    delta=first.number()-original[0].pitch.number()
    if ref.treatment in ('opening_fragment','callback') and delta%12:return ()
    result=[]
    from generator.solo.leads import available
    for template,n in zip(templates,original):
      target=n.pitch.number()+delta
      p=next((p for p in available(harmony,template.start,template.end,members=template.end-template.start>=2) if p.number()==target),None)
      if p is None:return ()
      result.append(dataclasses.replace(template,pitch=p))
    return (tuple(result),)
  paths=[]
  if ref.treatment == 'return':
    from generator.solo.leads import available
    delta=first.number()-original[0].pitch.number()
    direct=[]
    for template,n in zip(templates,original):
      p=next((p for p in available(harmony,template.start,template.end,members=template.end-template.start>=2) if p.number()==n.pitch.number()+delta),None)
      if p is None: break
      direct.append(dataclasses.replace(template,pitch=p))
    if len(direct)==count: paths.append(tuple(direct))
  end_template=templates[count-1]
  source_motion=original[-1].pitch.number()-original[0].pitch.number()
  for target in pitches(harmony,end_template,first.number()+source_motion,limit=4):
    template=tuple(dataclasses.replace(n,pitch=first if i==0 else target) for i,n in enumerate(templates[:count]))
    paths.extend(r.notes for r in routes.candidates(template,{template[-1].event_id},harmony,library,harmony.profile.register,'seed '+ref.id,purpose='entrance'))
  valid=[p for p in paths if not references.feature_error(feature(ref,p),p)]
  return sequences.diverse(valid,lambda ns:(routes.path_cost(ns),policy.stable_rank(ref.id,ns)),
    lambda ns:routes.path_family(ns,harmony),4)


@dataclasses.dataclass(frozen=True)
class Unit:
  notes: tuple[types.Note,...]
  feature: types.IdentifyingFeature
  reference: types.SourceReference
  operation: str
  anchor: types.Anchor
  score: float
  source: str
  routes: tuple[types.RouteCandidate,...] = ()
  start: F = F()
  end: F = F()


def unit_candidates(ref,start,finish,incoming,harmony,library,rhythms,meter,context,*,home=None,operation='introduce',terminal=False,batch=0,ending=None,goal=None):
  # History is evaluated by the caller after retrieving these concrete options.
  # Every state component used to construct this pool is in its cache key.
  if not hasattr(harmony,'fingerprint'):harmony.fingerprint=policy.stable_rank('harmony',(harmony.choices,harmony.profile))
  key=('theme-unit',ref,start,finish,incoming.last,incoming.direction,incoming.treatments,incoming.history,home,operation,ending,goal,batch,harmony.fingerprint,id(library),id(rhythms),policy.DEFAULT)
  if key in context.results:
    context.diagnostics['cache_hits']+=1;return context.results[key]
  result=[]; count=len(ref.notes)
  jobs=[]
  for pattern,label in patterns(ref,start,finish,rhythms,meter,context,home=home,operation=operation,terminal=terminal,ending=ending):
    if len(pattern)<count or len(pattern)>16:continue
    templates=tuple(types.Note(start+a,start+b,ref.notes[0].pitch,tuple(s for n in ref.notes for s in n.sources),
      'theme',event_id=f'{ref.id}:{start}:{i}') for i,(a,b) in enumerate(pattern))
    base=incoming.last.pitch.number() if incoming.last else harmony.profile.reference if harmony.profile.reference is not None else ref.notes[0].pitch.number()
    firsts=pitches(harmony,templates[0],base,limit=6 if batch else 3)
    targets=(ending.pitch,) if ending else pitches(harmony,templates[-1],goal if goal is not None else base,members=True,limit=policy.DEFAULT.theme_destinations,incoming=incoming)
    for first in firsts:
      for target in targets:
        # Rank joint jobs, retaining rhythm and destination coverage before
        # expensive path instantiation. The budget is spent on complete routes.
        rank=harmony.profile.cost(first.number())+max(0,abs(first.number()-base)-5)/12+phrasing.destination_cost(target,templates[-1].start,templates[-1].end,harmony,incoming,goal if goal is not None else base,terminal)
        jobs.append((rank,templates,label,first,target))
  jobs.sort(key=lambda j:(j[0],policy.stable_rank(ref.id,(j[1],j[3],j[4]))))
  selected=[];rhythm_seen=set();target_seen=set();entry_seen=set();degrees_seen=set()
  for job in jobs:
    family=phrasing.destination_family(job[4],job[1][-1].start,harmony)
    if family not in degrees_seen:
      selected.append(job);degrees_seen.add(family)
  for job in jobs:
    rhythm=tuple((n.start,n.end) for n in job[1]);target=job[4].number();entry=job[3].number()
    if rhythm not in rhythm_seen or target not in target_seen or entry not in entry_seen:
      if job not in selected:selected.append(job)
      rhythm_seen.add(rhythm);target_seen.add(target);entry_seen.add(entry)
  job_limit=policy.DEFAULT.theme_route_jobs*(batch+1)
  for job in jobs:
    if len(selected)>=job_limit:break
    if job not in selected:selected.append(job)
  for _,templates,label,first,target in selected[:job_limit]:
      proposed=[]
      if home and operation in ('repeat_with_harmonic_adaptation','return') and len(templates)==len(home.notes):
        heard=instantiate(templates,first,home.degree_steps,harmony)
        if heard and heard[-1].pitch==target:proposed.append((heard,()))
      for prefix in prefix_paths(templates,ref,first,harmony,library)[:2+batch]:
        if len(prefix)==len(templates):
          if prefix[-1].pitch==target:proposed.append((prefix,()))
          continue
        tail=(prefix[-1],*templates[count:])
        tail=(*tail[:-1],dataclasses.replace(tail[-1],pitch=target))
        for route in routes.candidates(tail,{tail[-1].event_id},harmony,library,harmony.profile.register,operation+' '+ref.id,purpose=rhythmic_purpose(operation,terminal))[:3+batch]:
          proposed.append(((*prefix[:-1],*route.notes),(route,)))
      seen=set()
      for actual,connections in proposed:
        identity=tuple(n.pitch.number() for n in actual)
        if identity in seen:continue
        seen.add(identity)
        core=actual[:count]; contract=feature(ref,core,treatment=operation if operation!='introduce' else None)
        if references.feature_error(contract,actual):continue
        last=actual[-1]
        if last.pitch.number()%12 not in harmony.members(last.start,last.end):continue
        checked=harmony.evaluate(actual,until=finish,complete=True)
        if not checked.valid:continue
        entry=max(0,abs(first.number()-incoming.last.pitch.number())-5)/12 if incoming.last else 0.
        leaps=sum(max(0,abs(b.pitch.number()-a.pitch.number())-5)/12 for a,b in zip(actual,actual[1:]))/max(1,len(actual)-1)
        direction=min(1,abs(last.pitch.number()-goal)/12) if goal is not None else 0.
        # Activity belongs to the complete phrase; contracts are pass/fail.
        score=harmony.profile.cost(profiles.weighted_center(actual))+2*checked.exposure+entry+leaps+phrasing.destination_cost(last.pitch,last.start,last.end,harmony,incoming,goal,terminal)
        anchor=ending or types.Anchor(last.event_id+':arrival',last.start,last.start,last.pitch,harmony.members(last.start,last.end),harmony.profile.register,
          last.end-last.start,'intermediate',harmony.at(last.start).chord,hold_until=last.end)
        score+=.25*rhythm_cost(tuple((n.start-start,n.end-start) for n in actual),finish-start,rhythmic_purpose(operation,terminal))
        result.append(Unit(actual,contract,ref,operation,anchor,score,label,connections,start,finish))
  unique={tuple((n.start,n.end,n.pitch) for n in u.notes):u for u in result}
  selected=sequences.diverse(tuple(unique.values()),lambda u:(u.score,policy.stable_rank(ref.id,u.notes)),
    lambda u:(u.notes[0].pitch.number()//12,u.notes[-1].pitch.number(),tuple(n.end-n.start for n in u.notes[:count])),policy.DEFAULT.theme_unit_alternatives)
  context.diagnostics['generated_candidates']+=len(selected)
  context.results[key]=selected
  return selected


def home_reference(home,operation):
  # A return refers to the opening the listener heard, not whichever later
  # three-note turn happens to rank best. Development may use its smaller core.
  notes = home.signature or home.notes[:min(4, len(home.notes))]
  if operation not in ('return', 'repeat_with_harmonic_adaptation'):
    notes = notes[:3]
  origin=notes[0].start
  notes=tuple(dataclasses.replace(n,start=n.start-origin,end=n.end-origin) for n in notes)
  treatment='return' if operation=='return' else 'rhythmic_seed' if operation in ('repeat_with_harmonic_adaptation','fragment','develop_rhythm') else 'contour_seed'
  return types.SourceReference(home.id,home.parent,home.source_start,home.source_start+home.duration,notes,treatment)


def make_home(unit,harmony,start=None,end=None):
  from generator.solo.realization import make_identity
  start=unit.notes[0].start if start is None else start
  identity=policy.stable_rank('solo-theme',(unit.reference.id,unit.notes))[:16]
  home=make_identity('solo_theme_'+identity,unit.reference.id,unit.notes,start,unit.notes[-1].end if end is None else end,'introduce',harmony)
  return dataclasses.replace(home,degree_steps=relative_steps(unit.notes,harmony),signature=home.notes[:len(unit.reference.notes)])


def unit_end(source,cursor,home,ending,bar):
  """Bound search by time without cutting the heard signature at a barline."""
  length=2*bar
  if home and home.signature:
    length=home.signature[-1].end
    while 0<length<bar:
      length+=home.signature[-1].end
    length=min(2*bar,max(bar,length))
  finish=min(source.end,cursor+length)
  if source.end-finish<bar+2 or ending.earliest<finish:
    finish=source.end
  return finish


def phrase_candidates(source,analysis,incoming,part,harmony,library,rhythms,meter,tempo,context,seed,*,stage='elaborated',batch=0,final=False,solo_end=None):
  from generator.solo import leads,realization
  if source.end-source.start<2:
    return short_fragment(source,incoming,part,harmony,tempo,seed,final)
  bar=F(meter.split('/')[0])*4/int(meter.split('/')[1])
  solo_end=solo_end or max(c.span.end for c in harmony.choices)
  head=source_notes(analysis)
  seed_key=('source-seeds',analysis,bar,seed)
  if seed_key not in context.pools:context.pools[seed_key]=seeds(analysis,bar,seed)
  roots=context.pools[seed_key]
  ending_options=phrasing.endings(source,incoming,part,harmony,bar,limit=8*(batch+1),final=final)
  states=[(0.,(),incoming.home,incoming,ending) for ending in ending_options]
  while states and any(not units or units[-1].end<source.end for _,units,_,_,_ in states):
    next_states=[]
    for cost,units,home,state,ending in states:
      cursor=units[-1].end if units else source.start
      if cursor>=source.end:
        next_states.append((cost,units,home,state,ending))
        continue
      finish=unit_end(source,cursor,home,ending,bar)
      introducing=home is None
      if introducing:
        requests=[(r,'introduce') for r in roots]
      else:
        operations=['continue'] if finish==source.end and cursor>source.start else ['develop_contour','develop_rhythm']
        if cursor==source.start:operations.append('return')
        requests=[(home_reference(home,op),op) for op in operations]
        # A uniform duration alone is not identifying musical evidence.
        requests=[(r,op) for r,op in requests if op!='develop_rhythm' or len({n.end-n.start for n in r.notes})>1 or any(a.end!=b.start for a,b in zip(r.notes,r.notes[1:]))]
        if cursor>=8*bar and cursor==source.start and incoming.callbacks<2:
          requests.extend((dataclasses.replace(r,treatment='callback'),'callback') for r in roots[:1] if r.end-r.start<=bar)
      for ref,operation in requests:
        if introducing and source.end-source.start<2*bar and ending.earliest-cursor<ref.notes[-1].end:
          # A missing-harmony boundary can leave less than one full statement.
          # Declare a smaller contour seed; never pretend it proves the full motif.
          count=min(3,int(2*(ending.earliest-cursor)),len(ref.notes))
          if count<2:
            if len(ref.notes)!=1:continue
            n=dataclasses.replace(ref.notes[0],end=min(ref.notes[0].end,F(1),ending.earliest-cursor))
            ref=dataclasses.replace(ref,id=ref.id+':constrained_pitch',notes=(n,),treatment='opening_fragment')
          else:
            ref=dataclasses.replace(ref,id=ref.id+':constrained_contour',notes=ref.notes[:count],treatment='contour_seed')
        if operation=='continue' and state.notes:
          recent=state.notes[-min(3,len(state.notes)):]
          origin=recent[0].start
          ref=dataclasses.replace(ref,notes=tuple(dataclasses.replace(n,start=n.start-origin,end=n.end-origin) for n in recent),treatment='contour_seed')
        if ref.notes[-1].end>finish-cursor:
          reduced=tuple(n for n in ref.notes if n.end<=finish-cursor)
          if len(reduced)<2:continue
          ref=dataclasses.replace(ref,notes=reduced,treatment='contour_seed')
          operation='continue'
        terminal=finish==source.end
        base=state.last.pitch.number() if state.last else ref.notes[0].pitch.number()
        goal=ending.pitch.number() if terminal else round(base+(ending.pitch.number()-base)*float((finish-cursor)/(source.end-cursor)))
        options=unit_candidates(ref,cursor,finish,state,harmony,library,rhythms,meter,context,home=home,operation=operation,
          terminal=terminal,batch=batch,ending=ending if terminal else None,goal=goal)
        for unit in options:
          if introducing and similarity.near_copy(unit.notes,head,cursor,finish)['near_copy']:
            context.diagnostics['near_copy_rejections']=context.diagnostics.get('near_copy_rejections',0)+1;continue
          actual_home=home or make_home(unit,harmony,cursor,finish)
          figure=phrasing.heard(unit.notes,operation,unit.anchor,bar)
          repetition=phrasing.repetition(figure,state.history,bar)
          appearance=phrasing.appearance_cost(operation,state,cursor,solo_end) if home else 0.
          history=phrasing.remember(state.history,figure,bar)
          following=dataclasses.replace(state,home=actual_home,last=unit.notes[-1],notes=unit.notes,source_reference=state.source_reference or ref,
            history=history,returns=(*state.returns,*((cursor,) if operation=='return' else ())),
            register_peak=max(state.register_peak,*(n.pitch.number() for n in unit.notes)))
          next_states.append((cost+float(finish-cursor)*(unit.score+.8*repetition+appearance),(*units,unit),actual_home,following,ending))
    def rank(value):
      cost,units,home,state,ending=value
      elapsed=units[-1].end-source.start
      return cost/max(.001,float(elapsed)),policy.stable_rank(seed,tuple(u.notes for u in units))
    states=sequences.diverse(next_states,rank,
      lambda v:(v[2].id,v[4].pitch.number(),v[4].duration,len(v[1][-1].notes),v[1][-1].operation),policy.DEFAULT.theme_continuations)
    if not states:return ()
  result=[]
  for cost,units,home,state,ending in states:
    plain=tuple(n for u in units for n in u.notes)
    if similarity.near_copy(plain,head,source.start,source.end)['near_copy']:
      context.diagnostics['near_copy_rejections']=context.diagnostics.get('near_copy_rejections',0)+1;continue
    features=tuple(u.feature for u in units)
    # Cell tails are not compulsory melodic arrivals. Only the selected close
    # has a sounding contract; intermediate turns remain editable.
    anchors=(ending,)
    tails=(types.SustainedTail(ending.earliest,ending.hold_until,ending.pitch.number()),)
    options=[(plain,(),())]
    if stage=='elaborated':
      for actual,edit,route in leads.elaborate(plain,features,harmony,library,rhythms,meter,source,sustain_entry=True,tails=tails):
        options.append((actual,(edit,),(route,)))
    for notes,edits,selected_routes in options:
      identifier=part+'_'+source.id+'_'+policy.stable_rank(seed,leads.signature(notes))[:12]
      transforms=tuple(types.Transformation(identifier+f':{i}',u.reference.id,home.id,u.operation,u.notes[0].start,u.notes[-1].end,
        tuple(n.event_id for n in notes if u.notes[0].start<=n.start<u.notes[-1].end),tuple((n.start-u.notes[0].start,n.end-u.notes[0].start) for n in notes if u.notes[0].start<=n.start<u.notes[-1].end),preserves=(),source=u.reference.id+'; rhythm '+u.source) for i,u in enumerate(units))
      source_ref=state.source_reference
      draft=types.MelodicDraft(identifier,source.start,source.end,notes,transforms,(),(),anchors,home,'introduce' if not incoming.home else 'develop',
        features=features,reference=source_ref.id,reference_motif=home,source_phrase=source,source_reference=source_ref,
        source_links=tuple((n.event_id,n.sources) for n in notes),sustained_tails=tails)
      motif=types.Motif(home.id,home.notes,home.duration,(), 'realized solo theme from '+source_ref.id)
      landmark=types.Landmark(ending.earliest,ending.latest,ending.pitch.number(),ending.pitch.number(),0,'sustained destination')
      plan=types.PhrasePlan(identifier,source.start,source.end,motif,draft.relationship,'thematic_recomposition',None,harmony.profile.register,F(5,4),
        source.end-ending.hold_until,phrasing.activity(source,ending),(landmark,), 'sustain','closed',seed,
        source.id,source.start,source.end,(anchors,))
      before_rhythm=draft
      from generator.solo import gesture_rhythm
      if stage=='elaborated':
        draft,rhythm_edits=gesture_rhythm.revise(draft,harmony,incoming.treatments)
        notes=draft.notes;edits=(*edits,*rhythm_edits);transforms=draft.transformations
      phrase=realization.checked_phrase(plan,draft,notes,incoming.treatments,incoming,harmony,tempo,edits)
      if phrase is None:continue
      score=phrasing.evaluate(notes,incoming,harmony,source.start,source.end,bar)+.1*gesture_rhythm.fragmentation(notes)
      score+=sum(phrasing.destination_cost(u.anchor.pitch,u.anchor.earliest,u.anchor.hold_until,harmony,incoming,phrasing.register_goal(incoming,part,u.notes[0].pitch.number(),harmony.profile),u.anchor.role=='terminal') for u in units)/len(units)
      appearance_state=incoming
      for unit in units:
        score+=phrasing.appearance_cost(unit.operation,appearance_state,unit.notes[0].start,solo_end)/len(units)
        if unit.operation=='return':
          appearance_state=dataclasses.replace(appearance_state,returns=(*appearance_state.returns,unit.notes[0].start))
      score+=.05*phrase.state.travel/max(1,len(notes))/2000
      history=incoming.history
      for transform in transforms:
        group=tuple(n for n in notes if n.event_id in transform.events)
        if group:history=phrasing.remember(history,phrasing.heard(group,transform.operation,ending if group[-1].end==ending.hold_until else None,bar),bar)
      current=dataclasses.replace(phrase.state,next_destination=phrasing.next_destination(ending,harmony),home=home,source_reference=source_ref,callbacks=incoming.callbacks+sum(u.operation=='callback' for u in units),
        history=history,returns=state.returns,closures=incoming.closures+1,register_peak=max(state.register_peak,*(n.pitch.number() for n in notes)))
      if not incoming.home:
        introduced=tuple(n for n in notes if n.start<units[0].notes[-1].end)
        heard=dataclasses.replace(home,notes=tuple(dataclasses.replace(n,start=n.start-source.start,end=n.end-source.start,position=None) for n in introduced),
          degree_steps=relative_steps(introduced,harmony),signature=tuple(dataclasses.replace(n,start=n.start-source.start,end=n.end-source.start,position=None) for n in introduced[:len(units[0].reference.notes)]))
        current=dataclasses.replace(current,home=heard,themes=(heard,))
      source_control=leads.shift(source.notes,next((o for o in (0,1,-1,2,-2) if all(41<=n.pitch.number()+12*o<=76 for n in source.notes)),0))
      original=dataclasses.replace(draft,id=identifier+':source',notes=source_control,features=(),anchors=(),structural=(),sustained_tails=())
      refined=dataclasses.replace(draft,id=identifier+':plain',notes=plain)
      result.append(dataclasses.replace(phrase,score=score,state=current,initial=original,refined=refined,before_rhythm=before_rhythm,routes=(*tuple(r for u in units for r in u.routes if all(any((n.event_id,n.start,n.end,n.pitch)==(a.event_id,a.start,a.end,a.pitch) for a in notes) for n in r.notes)),*selected_routes)))
  return sequences.diverse(result,lambda p:(p.score,policy.stable_rank(seed,p.draft.id)),
    lambda p:(p.state.home.id,p.state.last.pitch.number(),p.anchors[-1].duration,len(p.state.returns)),policy.DEFAULT.phrase_alternatives)